1. Field of the Invention
The present invention relates to an organic electro luminescence display device, and more particularly to an organic electro luminescence display device that is adaptive for preventing the deterioration of its light emitting efficiency and picture quality, and a fabricating method thereof.
2. Description of the Related Art
Recently, there have been developed a variety of flat panel display devices that can reduce their weight and size, which are a disadvantage of a cathode ray tube CRT. The flat panel display device includes a liquid crystal display LCD, a field emission display FED, a plasma display panel PDP and an electro luminescence EL display device.
Studies for increasing the picture quality and the size of the screen of the flat panel display device have been actively in progress. The EL display device among these is a self-luminous device which emits light by itself. The EL display device excites a phosphorus material by use of a carrier such as electrons and holes, thereby displaying a video image.
The EL display device is largely divided into an inorganic EL display device and an organic EL display device in accordance with a material used.
The organic EL display device is driven with a low voltage of about 5˜20V in comparison with the inorganic EL display device which requires a high voltage of 100˜200V so that a direct low voltage driving is possible. Further, the organic EL display device has excellent characteristics such as wide viewing angle, high speed response, high contrast ratio and so on, thus the organic EL display device can be used as a pixel of a graphic display and a pixel of a surface light source or a television image display, and the organic EL display device is a suitable next generation flat panel display because of its thinness and lightness and a good color sense.
FIG. 1 is a diagram briefly representing a general organic EL display device, FIG. 2 is a plane view specifically representing part (A area) of FIG. 1, and FIG. 3 is a sectional diagram illustrating a section of the organic EL display device which is cut along the lines I–I′ and II–II′ of FIG. 2.
The related art organic El display device shown in FIGS. 1 to 3 includes a display area P1 where there is formed an organic EL array inclusive of a driving electrode, e.g., anode electrode and cathode electrode, and a non-display area P2 where there is located a pad part 25 which supplies driving signals to the driving electrodes of the display area P1.
The organic EL array formed in the display area P1 has an anode electrode 4 formed on a substrate 2 and a cathode electrode 12 formed in a crossing direction to the anode electrode 4.
A plurality of anode electrodes 4 are formed on the substrate 2 to be separated from each other with a designated gap. An insulating film 6 having an aperture part is formed for each EL cell area on the substrate 2 where the anode electrode 4 is formed. Barrie ribs 8 are located on the insulating film 6 for separating an organic light emitting layer 10 and the cathode electrode 12 which are to be formed thereon. The barrier ribs 8 are formed in a direction of crossing the anode electrode 4 and have an overhang structure where an upper end part has a wider width than a lower end part. The organic light emitting layer 10 and the cathode electrode 12 formed of an organic compound are sequentially deposited over the entire surface of the insulating film 6 where the barrier ribs 8 are formed. The organic light emitting layer 10 has a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer and an electron injection layer deposited and formed on the insulating film 6.
In the non-display area P2, there are formed a first line 52 which is extended from a first electrode (or the anode electrode 4), data pads which supply a data voltage to the anode electrode 4 through the first line 52, a second line 53 which is connected to a second electrode (or the cathode electrode) 12, and a scan pad which supplies a scan voltage through the second line 53. Herein, an opaque conductive layer 52B for improving the conductivity of the second line 53 can be further formed on the second line 53. The data pad is connected to a TCP on which a first driving circuit generating the data voltage is mounted, to supply the data voltage to each anode electrode 4. The scan pad is formed at both sides of the data pad. The scan pad is connected to a TCP on which a second driving circuit generating a scan voltage is mounted, to supply the scan voltage to each cathode line 12.
The organic EL array of the display area P1 has a characteristic of being easily deteriorated by moisture and oxygen. In order to solve the problem, an encapsulation process is performed, thereby bonding a cap 28 and the substrate 2, where the organic EL array such as the anode electrode 2 is formed, together through a sealant 25 such as an epoxy resin. A getter for absorbing moisture and oxygen is filled in the center part of the rear surface, thereby protecting the organic EL array from the moisture and the oxygen.
In the related art organic EL display device having such a structure, if a voltage is applied between the anode electrode 4 and the cathode electrode 12 as shown in FIG. 4, an electron (or cathode) generated from the cathode electrode 12 moves toward the light emitting layer 10c through the electron injection layer 10a and the electron transport layer 10b. Further, a hole (or anode) generated from the anode electrode 4 moves toward the light emitting layer 10c through the hole injection layer 10e and the hole transport layer 10d. Accordingly, exitons are formed by a recombination of the electron and the hole which are supplied from the electron transport layer 10b and the hole transport layer 10b. The exitons are excited again to a ground state to emit a light of a fixed energy to the outside through the anode electrode 4, thereby displaying a picture.
On the other hand, in the organic EL display device, it often takes place that the sealant 25 flows into the organic EL array of the display area P1 through a space between the barrier ribs 8 when bonding the gap 28 and the substrate 2 together. The sealant 25 includes a lot of moisture, oxygen and impurities, thereby damaging the organic light emitting layer 10 of the organic EL array. Accordingly, there is a problem in that the light emitting efficiency and picture quality of the device is deteriorated.